The present invention relates to a brake booster, particularly for motor vehicles, including a booster casing, a movable wall disposed in the booster casing to divide the booster casing into a vacuum chamber and a working chamber, a control valve to control the pressure in the working chamber, the control valve casing being rigidly connected with the movable wall and arranged so as to be guided by the booster casing, at least one vacuum channel which connects the vacuum and the working chambers, and at least one outside air channel, the vacuum and air channels having a common channel section in the control valve which may be closed by the control valve.
Such a brake booster is disclosed in British Patent No. 1,546,853. In this brake booster, the movable wall forms an annular recess into which one of the end surfaces of the control casing is inserted. The control casing which may be either an all-metal or an all-plastic casing is connected with the movable wall by means of projecting bosses, which penetrate the movable wall in the manner of a snap fastener, or by means of bolts. The vacuum channel in this brake booster is passed through a conical head part to the valve and then, radially, through the wall of the casing outwards to the working chamber. This known brake booster features a relatively long constructional length. In addition, the hub of the control valve casing protrudes outwards, thus, having contact with unfiltered air which may lead to dirt accumulation.